The present invention generally concerns portable fluid heaters, and more specifically, an efficient, portable fluid heater that can also be used in the field to heat and sterilize water, to generate electrical power, and to heat a microclimate.
Outdoor enthusiasts, particularly those who enjoy backpacking and the like, frequently include items such as portable cook stoves, water bottles, and cooking utensils in the equipment that they carry in their pack. With the ever increasing availability of portable consumer electronics, it is becoming more and more common for such outdoor enthusiasts to also carry various consumer electronic devices when hiking. Global positioning satellite (GPS) receivers and cellular phones are two examples of electronic devices that outdoor enthusiasts often include in their gear. Particularly for backpacking enthusiasts, the size and weight of any equipment carried is of primary importance. Furthermore, equipment that is multifunctional is highly desirable, because such equipment can reduce the number of different pieces of gear.
Lightweight, portable cook stoves are well known in the art and are often required for overnight trips in wilderness areas where natural fuel is limited or where concerns about forest fires preclude building a campfire for outdoor cooking. Such stoves are available for use with a variety of different fuels, including white gas, butane/propane, kerosene, and other less common combustibles, such as hexamine fuel tablets. Generally such stoves are designed to support a cooking utensil, such as an appropriately sized metal pan or cup. While such devices are quite functional, they tend to be somewhat inefficient, as the flame first heats a portion of the cook stove, which in turn transfers heat to the cooking utensil holding the food or liquid to be heated. Often a significant portion of the cooking utensil is exposed to the ambient environment, so that a substantial portion of the thermal energy produced by the flame is transferred to the ambient environment, instead of to the food or liquid being heated.
It would therefore be desirable to provide a more efficient device to replace prior art cook stoves. Ideally, such a device should not require that a separate cooking utensil be employed for heating food or water. Furthermore, such a device should be more thermally efficient than prior art cook stoves, by minimizing the portion of thermal energy transferred to the ambient environment rather than to the food or liquid being heated. Preferably, such a device should be able to heat liquid within a conventional plastic water bottle of the type already commonly carried by outdoor enthusiasts, eliminating the need for carrying cooking utensils such as pots and/or pans.
Another item that is often carried when hiking is a portable water filter or other device for purifying or sterilizing water. Concerns about giardia and other potentially harmful bacteria that are frequently found in water sources have prompted people to either carry water from home, or to use such filters that eliminate bacteria larger than a given filter porosity from the water drawn out of streams or lakes. Those who are outdoors for extended periods of time will generally prefer to carry portable means for purifying water, in order to reduce the amount of potable water that must be carried. Also, devices that simply purify water by filtering out harmful bacteria will not have an effect on viral agents, as viruses are significantly smaller than bacteria. Several portable water treatment devices, including those disclosed in U.S. Pat. Nos. 5,273,649; 5,268,093; 5,244,579; and 3,635,799 have been developed for treating water from local sources, such as streams or lakes, so that it can be safely ingested. However useful these devices are, they require the outdoor enthusiast to include yet another item of equipment in the gear that is carried. While it is possible to simply boil water in a conventional pot over a conventional stove, it is desirable to eliminate gear that can be viewed as redundant. Thus, it would be desirable to provide a device that can be used for both heating water for cooking purposes and for sterilizing water, without requiring any pot.
A further item that is often used for outdoor activities is a warming device. For example, many outdoor enthusiasts and outdoor sports fans carry one or more hand warmers in addition to multiple layers of clothing. Some of theses hand warmers burn a carbon stick inside an insulated container that fits in a jacket pocket or at the foot of a sleeping bag. The amount of heat produced can not be easily regulated, and the carbon stick typically does not last more than an hour or two. As a result, the user may have to carry many carbon sticks if the user will be outdoors for a long time. Moreover, the heat produced is concentrated in a single area, such as a pocket, and does not readily provide heat to other portions of the outdoor enthusiast""s body. Other warming packs produce heat as a result of a chemical reaction, such as those packs used by skiers in jackets, gloves, and boots. However, again, the amount of heat produced can not be easily regulated, the heat-producing reaction typically does not last more than a few hours, and the heat is not uniformly distributed very far the warming pack. Thus, again the outdoor enthusiast must to carry multiple packs for extended periods outdoors or to warm various parts of the body. It would be desirable to utilize a single heating device, or at least the same type of fuel, for warming the outdoor enthusiast as well enabling the outdoor enthusiast to cook and boil drinking water.
Finally, as noted above, outdoor enthusiasts are likely to include portable consumer electronics such as GPS receivers and cell phones within the assortment of gear that they carry. To increase the operating time of such devices on trips that may extend over several days, additional batteries must be carried. However, spare batteries are relatively heavy and increase the number of pieces of equipment that must be carried. It would therefore be desirable to provide a device that can not only heat water for cooking, purify water as required, and keep the outdoor enthusiast warm, but can also recharge the batteries used in portable electronic devices.
The prior art does not teach or suggest a replacement for a portable device that can provide the multifunctional capabilities discussed above. It will therefore be apparent that such a device would have considerable utility for both outdoor sports and military-related activities.
In accord with the present invention, a portable water heating apparatus adapted to couple with a portable reservoir employed for carrying and storing water, and adapted to be used with a source of heat is defined. The apparatus includes a fluid heating channel adapted to be coupled in fluid communication with the portable water reservoir disposed above the heat exchanger, and a heat exchanger adapted to absorb thermal energy from a source of heat. The heat exchanger is disposed adjacent to and in thermal contact with the fluid heating channel so that heat is readily transferred from the heat exchanger to the fluid heating channel. Water disposed within the fluid heating channel is thus heated. The heated water and/or steam is introduced into the portable water reservoir. Heating of the water contained within the portable water reservoir continues until a desired temperature is achieved.
Preferably, the portable water reservoir has an opening at one end that is sealingly engaged by a cap included on the water heating apparatus, and the water reservoir is then inverted so that the opening sealed by the cap faces downward. The cap has a fluid inlet through which the heated water flows into the portable water reservoir from the fluid heating channel and a fluid outlet through which the cool water in a lower portion of the water reservoir flows into the fluid heating channel.
Preferably, a seal between the cap and the opening of the portable water reservoir fails at a predetermined pressure, thereby releasing excess pressure. In at least one embodiment, the predetermined pressure is at least approximately 10 psi. Also preferably, the fluid outlet includes a one-way valve, which permits water to flow out of the fluid outlet, but not in. Consequently, water disposed within the fluid heating channel can only exit through the fluid outlet. The one-way valve changes between an open state and a closed state in response to pressure conditions within the portable water reservoir and the fluid heating channel.
To reduce the weight of the device, the heat exchanger is preferably fabricated from a low density and thermally conductive metal. In at least one embodiment, the heat exchanger is preferably removably attached to the cap.
In one preferred embodiment, the apparatus includes a hot water outlet in fluid communication with the water reservoir so that hot water can selectively be removed from the portable water reservoir. A pressure relief valve designed to open at a predetermined pressure is optionally included. The predetermined pressure corresponds to a desired temperature, enabling water of the desired temperature to be automatically discharged through the hot water outlet.
A fluid channel coupled to the cap and having a first end and a second end is preferably included. The first end is coupled in fluid communication with the hot water outlet, and the second end is coupled in fluid communication with the upper portion of the portable water reservoir. Steam accumulating in the upper portion of the water reservoir can be removed from the water reservoir through the hot water outlet. In this embodiment, the heating apparatus includes a condenser adapted to be coupled to the portable water reservoir, which is usable to condense steam contained therein into liquid water, thereby providing purified potable water.
Preferably, the portable water reservoir is substantially transparent or translucent to visible light, so that a user can visually determine when water contained within the water reservoir boils. In at least one embodiment, the apparatus includes a temperature-sensing element usable for displaying a temperature of the water disposed within the water reservoir. A liquid crystal thermometer can be employed as the temperature-sensing element.
To generate electrical energy while heating water, some embodiments include a thermoelectric module that generates an electric current when exposed to a temperature differential. The thermoelectric module is disposed between the heat exchanger and the water reservoir, enabling a first surface of the thermoelectric module to be exposed to relatively cool water from the water reservoir, while a second and opposite surface is adjacent the heat exchanger. Preferably, the thermoelectric module includes electrical leads capable of being connected to supply an electrical current to an electrical device or a rechargeable battery.
The water heater can be used to heat water for cooking or for beverages and the like in a plastic portable water reservoir, to generate steam that can be condensed to provide purified potable water, and to generate electricity using the thermoelectric module. By suitably configuring the water heater apparatus, any combination of the above can be simultaneously executed.
Other aspects of the present invention are directed to methods for the water heater for the purposes noted above. These methods include steps that are generally consistent with the functions of the elements included in the apparatus described above.
Yet another aspect of the invention is directed to a portable apparatus for heating a microclimate. The portable apparatus comprises a portable microclimate heating article (PMCHA) that defines the boundaries of the microclimate, and a portable heating unit in fluid connection with the PMCHA. The PMCHA comprises an element that defines the structural configuration of the PMCHA, such as a wearable jacket, a sleeping bag, a tent, or other portable item. The PMCHA also comprises a delivery channel incorporated into the element to carry a heating fluid that transfers heat energy through the element to the microclimate. The portable heating unit is preferably small enough to carry on a belt and comprises a heat source; a heat exchanger disposed in proximity to the heat source; and a heating chamber coupled to the delivery channel and in proximity to the heat exchanger. The heat source provides heat energy to the heat exchanger, and the heat exchanger transfers heat energy to the heating fluid that flow through the heating chamber out to the delivery channel of the PMCHA. The heating fluid circulates between the heating chamber and the PMCHA.
A thermoelectric unit is also optionally located between the heat exchanger and the heating chamber. In this case, the heating fluid in the heating chamber is used as the cold heat sink and the heat exchanger is used as the hot heat source. The thermal transfer between the heat exchanger and the heating fluid in the heating chamber may not produce as much electrical energy as a the other embodiments that use a cold reservoir, but the temperature differential is still sufficient to produce electrical energy. The electrical energy may be provided to a pump in the portable heating unit that pumps the heating fluid through the PMCHA. The electrical energy may also be provided to a rechargeable battery, or other electrical device.
A further aspect of the invention is a method for heating a microclimate comprising the steps of incorporating a delivery channel into the PMCHA; thermally coupling the delivery channel to the portable microclimate heating unit; inserting a heating fluid into the delivery channel; heating the heating fluid with the portable microclimate heating unit; and causing the heating fluid to flow through the delivery channel of the PMCHA, thereby causing thermal energy to transfer from the heating fluid to the PMCHA defining the microclimate.